Some of us have never found a single dollar bill on the sidewalk. But once in a blue moon a lucky soul in the upper Midwest reaches down into the Ice Age deposits of our country and plucks out a diamond.

It doesn’t take much geologic knowledge to recognize a diamond in the rough as an interesting and valuable object.

Diamonds are the hardest mineral in the Earth, which means they will scratch quartz, window glass and even other hard gems like ruby and emerald.

And diamonds have a very high luster, a term referring to their ability to reflect light.

In short, it’s not too tough to identify diamonds, even before they have been shaped into cut gemstones.

That’s why, since the 1800s, farmers and other residents of the Midwest have occasionally spotted and scooped up a diamond when digging water wells or otherwise disturbing the ground.

Most diamonds are found near the place where deep Earth processes blasted them to the surface in special rock material called kimberlite (named for Kimberley, South Africa).

But there aren’t rocks like that in the Midwest.

Instead, the diamonds in that part of the world were transported to their resting places by the enormous glaciers that dominated North America during the Ice Age. Geologists spent generations looking for the ultimate source of the diamonds “up ice” in Canada.

It’s only recently that a few dedicated – not to say obsessed – geologists found the sources in northern Canada.

Geologists usually look for diamonds not by initially searching for diamonds themselves, but by looking for more common minerals that often come along with diamonds from their deepest sources in the Earth.

Even so, finding diamond-rich rocks is generally a needle-in-a-haystack challenge.

But, in time, dedicated exploration geologists found the source of diamonds in northern Canada that can – occasionally – be found in our upper Midwest.

The fascinating tale of the search is one you can read about in the book “Barren Lands” by Kevin Krajick.

Other people discover objects of no monetary value but that mean a lot to those of us interested in Earth history. That was the case earlier this summer when a contractor in Tennessee digging eight feet deep for a swimming pool unearthed a fossil.

It appears to be the jawbone of a trilophodon, an extinct relative of the mastodon.

Mastodons and their kin roamed the Earthduring the Ice Age – the same time that a few diamonds were arriving to the Midwest courtesy of Canadian sources.